Can I have MailStream Plus take one Name-Address input file, and separate the mail into multiple presorted Name-Address output files?

MailStream Plus™, all versions, all platforms
No, MailStream Plus™ (MSP) outputs all records in a job run into a single presorted Name-Address output file.
For separate output Name-Address files, you would have to separate the input records into files as desired, and run separate MSP jobs.

Also, there is only one Mail.dat file set produced for a MSP presort run.
UPDATED:  May 15, 2019